These worked well for me with 1,5GHZ, Geforce 3 128mb, and 768 mbit of memory.

OFP might not be to your liking as you are killed with one shot and thats it. Unreal Tournament 1 and 2, System Shock 2, Ghost Recon the first and its addons worked fine with my old P2-400 mhz so they should work fine with you pc. Both Thieves too. OFP might be a bit of a trouble as it takes loads of space on your hard disc...